function fbnq(){
    //0 1 2 3 4 5 6  7
    //1,1,2,3,5,8,13,21,34.55,89,144…
    var n = prompt("请输入要显示第几位斐波那契数",'');
    var arr = [1,1];
    for(var i=2; i<=n-1; i++){
        arr[i] = arr[i-2] + arr[i-1];
    }
    alert(arr[n-1]);
}
fbnq();